SPECTROSCOPIC AND MOLECULAR ORBITAL STUDIES OF CHROMOTROPIC TERNARY COMPLEXES OF COPPER(II) WITH THENOYLTRIFLUOROACETONE AND DIAMINE DERIVATIVES

摘要

New ternary complexes of copper(II) with thenoyltrifluoroacetone (HTTA) and some derivatives of diamines (diam) (N,N, N'.N'-tetramethylethylenediamine (Me_4en), N,N,N'-trimethylethylenediamine (Me_3en), N,N,N'-triethylethylenediamine (Et_3en) and N-methyl-1,4-diazacycloheptane (medach)) of the general formula Cu(TTA)(diam)X where X = ClO_4~- or Cl~- have been prepared. Spectral analyses, molecular orbital calculations, based on a semiempirical method using PM3 calculations, and magnetic studies have been carried out to characterize the structures and chromotropicity of these complexes. The results along with the analytical data are in favor of square-planar or trigonal bipyramid geometries for the perchlorate and chloride complexes, respectively, in either the solid state or a solution of weak donor solvents. On the other hand, an octahedral structure is identified when using strong donor solvents. Perchlorate complexes show a remarkable color change from violet to green in different solvents and anions as their donor strengths increase. Whereas the chloride complexes are highly affected by the acceptor properties of the solvents and values of the oscillator strengths (f), indicating that, the visible d-d transition probability of these complexes decrease as the donor number of the solvent interaction increases. Molecular orbital calculations for these complexes were found to be consistent with the experimental results. The spectral studies refer to the importance of these complexes as Lewis acid-base color indicators for the donor strength of both solvents and anions.